A grating is an arrangement consisting of a large number of parallel slits of same width and separated by equal opaque spaces.

• It is obtained by ruling equidistant parallel lines on a glass plate with the help of a diamond.
• The lines act as opaque spaces and the incident light cannot pass through them.The space between the two lines is transparent to light and acts as a slit.
• The spacing between the lines is of the order of wavelength of visible light.The number of a lines in a plane transmission grating is of the order of 15000 to 20000 per inch.
• The width of each slit is a and opaque spacing between two consecutive slits is. b.
• (a+b) is called grating element or grating constant.
• It can be seen that distance between two consecutive slits is grating element.

Diffraction grating is an optical component with a periodic slits of equal

It is manufactured by drawing parallel lines on glass plate using a fine diamond point.

The etched lines act as opaque spacing and the glass between the two lines act as slit.

Width of each slit and the opaque space combined is called grating element.

Gratings are used to determine the wavelength of light by means of diffraction.